//var a = 10;
//console.log(a);
//ctrl + j 打开终端
//cd Day03进入目录
//node+空格+Tab
console.log(a);//undefined
var a = 10;
var a = 20;
var a = 'hello';
console.log(a);
/**
 * js多行注释
 * 解析顺序 因为使用var声明变量会进行变量提升
 * var a;
 * console.log(a)
 * a = 10;
 */